Question: Solve for $x$ and $y$ using substitution. ${-2x-3y = 0}$ ${x = -6y-9}$
Since $x$ has already been solved for, substitute $-6y-9$ for $x$ in the first equation. ${-2}{(-6y-9)}{- 3y = 0}$ Simplify and solve for $y$ $12y+18 - 3y = 0$ $9y+18 = 0$ $9y+18{-18} = 0{-18}$ $9y = -18$ $\dfrac{9y}{{9}} = \dfrac{-18}{{9}}$ ${y = -2}$ Now that you know ${y = -2}$ , plug it back into $\thinspace {x = -6y-9}\thinspace$ to find $x$ ${x = -6}{(-2)}{ - 9}$ $x = 12 - 9$ ${x = 3}$ You can also plug ${y = -2}$ into $\thinspace {-2x-3y = 0}\thinspace$ and get the same answer for $x$ : ${-2x - 3}{(-2)}{= 0}$ ${x = 3}$